Underground work, including underground mining, has been a historically dangerous, but critical, commercial activity. For example, the hazards involved in underground mining include suffocation, gas poisoning, roof collapse and gas explosions. Nonetheless, underground mining continues to account for approximately 60% of world coal production and other important resources. Although there have been significant improvement in underground mining safety, underground mining accounts for thousands of fatalities per year in foreign countries, and thousands of injuries and dozens of fatalities in the United States.
Of particular concern is the ability to sustain the lives of underground workers for a period of time if they become trapped underground or if the atmosphere of the underground atmosphere becomes dangerous. However, current safety devices have proven to be of limited value in sustaining the lives of groups of underground workers for the time necessary for rescue operations due to a number of factors including logistics, accessibility, protection and sustainability. Accordingly there is a continuing need for improved safety in the area of underground mining, in the United States and abroad.